<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>二级下拉菜单</title>
<style type="text/css">
*{
	margin: 0;
	padding: 0;
	list-style: none;
}
#one>li{
	width: 80px;
	height: 40px;
	margin: 2px;
	background: #d8d8d8;
	float: left;
	text-align: center;
	line-height: 40px;
}
.two{
	width: 80px;
	height: 160px;
	background: #666;
	display: none;
}
</style>
<script type="text/javascript">
	window.onload=function(){
		var oUl=document.getElementById('one');
		var aLi=oUl.children;//获取第一级菜单的四个子标签
		for (i=0;i<aLi.length;i++) {
			aLi[i].onmouseover=function(){
				this.children[0].style.display='block';
			};
			aLi[i].onmouseout=function(){
				this.children[0].style.display='none';
			};
		}
	};
</script>
</head>
<body>
<ul id="one">
	<li class="one_list">一级菜单
		<ul class="two">
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
		</ul>
	</li>
	<li class="one_list">一级菜单
		<ul class="two">
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
		</ul>
	</li>
	<li class="one_list">一级菜单
		<ul class="two">
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
		</ul>
	</li>
	<li class="one_list">一级菜单
		<ul class="two">
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
			<li>二级菜单</li>
		</ul>
	</li>
</ul>
</body>
</html>